Field of the Invention
The present invention relates to a printed circuit board and an image forming apparatus.
Description of the Related Art
As an electrophotographic image forming apparatus configured to form an image on a recording material, there is hitherto known a copying machine, a laser beam printer, and so on. A tandem type color copying machine is mentioned as an example of the electrophotographic image forming apparatus. The image forming apparatus is equipped with a power supply device, which converts an AC voltage supplied from a commercial power source into a DC voltage so as to supply power required for operating the image forming apparatus. When a high withstand voltage cable is used for connection between an output portion of a high voltage power supply substrate of the power supply device and each portion of a main body of the main body of the image forming apparatus, it takes much time for assembly in the factory, and cable cost is high. Therefore, there is proposed a structure of direct connection without using a cable, in which contacts are formed on the high voltage power supply substrate, and the high voltage power supply substrate is assembled to the main body of the image forming apparatus, so as to directly connect the contact portions of the high voltage power supply substrate to contacts of the image forming apparatus (Japanese Patent Application Laid-Open No. 2002-158408).
For instance, in a high voltage power supply substrate 700 as illustrated in FIGS. 5A, 5B, and 5C, contact portions 701 (701y, 701m, 701c, and 701k) and a signal connector 704 are provided on a component surface 700a of the high voltage power supply substrate 700. The high voltage power supply substrate 700 illustrated in FIG. 5A is assembled to the main body of the image forming apparatus so that the component surface 700a of the high voltage power supply substrate 700 is on a far side of the main body of the image forming apparatus while a pattern surface 700b of the high voltage power supply substrate 700 is on a near side of the main body of the image forming apparatus. Therefore, from the pattern surface 700b of the high voltage power supply substrate 700, an assembling worker needs to connect a signal wire to the signal connector 704 so that workability may be decreased and the working process may be made difficult. Therefore, there is proposed a high voltage power supply substrate 800 as illustrated in FIGS. 6A, 6B, and 6C, for example. However, in the high voltage power supply substrate 800 illustrated in FIG. 6A, spring contacts 803 (803y, 803m, 803c, and 803k) are brought into contact with jumper wires 1003 and 1004 from the side of a pattern surface 800b as illustrated in FIG. 6C. Therefore, the jumper wires 1003 and 1004 may come out from solder portions 1006 and 1007. Therefore, there is proposed a high voltage power supply substrate 900 as illustrated in FIG. 7B. In the high voltage power supply substrate 900 illustrated in FIG. 7B, even when a pressure force of a spring contact 913 is exerted on jumper wires 1103 and 1104, the jumper wires 1103 and 1104 do not come out from solder portions 1106 and 1107. Detailed descriptions of FIGS. 5A to 5C, 6A to 6C, and 7A to 7C will be provided later.
However, in FIG. 7A, the spring contact 913 of the main body of the image forming apparatus is brought into contact with the jumper wires 1103 and 1104 of the high voltage power supply substrate 900 on the side of a pattern surface 900b of the high voltage power supply substrate 900. In addition, the jumper wires 1103 and 1104 are soldered on the pattern surface 900b of the high voltage power supply substrate 900. In a case where the high voltage power supply substrate 900 is a single-sided substrate, it is necessary to manually solder the jumper wires 1103 and 1104 to the high voltage power supply substrate 900 to form the solder portions 1106 and 1107 after other components 1110 are soldered on the high voltage power supply substrate 900 through a so-called flow soldering process in which the substrate is caused to pass a solder bath filled with liquid solder.
FIG. 7C is an enlarged view of a vicinity of the contact portion in the structure illustrated in FIG. 7A and FIG. 7B. When the jumper wires 1103 and 1104 are soldered on the high voltage power supply substrate 900, flux for solder (hereinafter referred to as solder flux) may flow from solder portions 1106, 1107, 1108, and 1109 along surfaces of the jumper wires 1103 and 1104 in directions indicated by the arrows. The solder flux is used for chemically removing an oxide film on a metal surface to be soldered to provide a metal surface for soldering. When the solder flux flows to portions of the jumper wires 1103 and 1104 contacting the spring contact 913, a good contact state between the spring contact 913 and the jumper wires 1103 and 1104 may not be secured. Then, a desired high voltage may not be supplied from the high voltage power supply substrate 900 to a load such as a primary transfer roller. As a countermeasure to this drawback, it is considered to provide a step of cleaning the solder flux adhered to the jumper wires 1103 and 1104. However, when the solder flux remains after the cleaning because of a variation of the cleaning work level, the good contact state between the spring contact 913 and the jumper wires 1103 and 1104 cannot be secured as described above. The problem that the good contact state of the spring contact cannot be secured because of a flow of the solder flux can also occur when the contact portion is formed by a contact plate instead of the jumper wire.